The present invention relates to a preventive agent to be used for the prevention of polymer scale occurring on the inside face of polymerization reactor at the time of, for example, polymerization of vinyl type monomers.
When polymerizing vinyl type monomers in the presence of dispersant or emulsifier and polymerization initiator, solid polymer called scale is frequently stuck onto the inside faces of polymerization reactor, that is, inner wall thereof, wings of agitator, baffle plate, condenser, etc.
This scale brings about a lot of disadvantages such as lowering in the heat transfer efficiency, reduction in the product yield, lowering in the quality due to the incorporation of peeled scale into product, labor necessary for the removal of scale and decrease in the productivity accompanying the waste of time necessary for this, occurrence of the problems on the labor safety and hygiene of workers, etc.
In order to dissolve these problems, many methods have been proposed for the prevention of the formation of scale and the sticking thereof onto the polymerization vessel.
For instance, there are methods to coat dyes, pigments and other organic polar compounds, mineral acids and salts thereof, multivalent metallic salts, etc. onto the inside face of polymerization vessel or to add these to aqueous medium, but these methods have various shortcomings that the persistence of the effect is difficult, the characteristics of the product become poor or the like.
As an improved method for these, a method to coat high molecular compounds with functional group possible to prevent the formation of scale on the inside face of polymerization vessel is also proposed.
Phenolic compounds have been used hitherto as the polymerization inhibitors, and many methods utilized these compounds are also proposed.
For instance, methods are disclosed to coat such substances onto the inside face of polymerization vessel as reaction resultant of initial condensate of phenol-aldehyde with nitrophenol in Japanese Unexamined Patent Publication No. 160004/1980, self-condensed polyhydric phenol and polyhydric naphthol in U.S. Pat. No. 4,080,173, condensates of phenolic compounds with aromatic aldehydes in Japanese Unexamined Patent Publication No. 54317/1980, ester of propylene glycol with alginic acid in Japanese Unexamined Patent Publication No. 102610/1980, nitrile-containing polymers in Japanese Unexamined Patent Publication No. 101889/1979, modified rosins in Japanese Unexamined Patent Publication No. 7401/1983, resin extracted from pine tree in Japanese Unexamined Patent Publication No. 168601/1983, reaction products between drying oil or semidrying oil, phenolic compounds and, if necessary, aldehydes in Japanese Unexamined Patent Publication No. 204006/1983, and so on.
However, with these methods, there are many points to be improved, for instance, that the polymerization velocity decreases, that the problems are caused in the persistence of descaling effect because of the insufficiency of durability in the coated film, etc.
As a result of diligent studies to dissolve these shortcomings, the inventors have found that, when certain sorts of organic polymers are coated onto the inside face of polymerization vessel and the polymerization is conducted, they prevent the scale remarkably from sticking at the time of the polymerization of, in particular, vinyl type monomers and they are extremely excellent in the adherence to metal, leading to the completion of the invention.